Last week started having an issue in that I could not access a clients Exchange 2016 server EAC/ECP management pages from a remote PC – it was fine on the server itself.

It seems to have started after a recent Exchange or Windows update DISABLED all Exchange and IIS services …. but never turned them back to AUTOMATIC Start – that took some diagnosing and troubleshooting to work out what 30 or 40 services I needed to change back to AUTO Start….. anyway all seemed OK until they rang about a issue accessing the ECP/EAC pages….

Bear in mind this is a hybrid 2013/2016 Exchange environment (Exch 2013 was ONLY used as a stop gap to go from Exch 2007 to Exch 2013 then to Exch 2016 as directly going from Ex 2007 to Ex 2016 is not possible = what a time waste, thanks Microsoft!) – although IO dont think it’s relavent here

Anyway – the IT person onsite has a link in their browser to login to ECP – https://mail.company.com.au/ecp and life was good – that stopped working after the above-mentioned ‘updates’ – the EP page would let them login but when it displayed it was all garbled and displayed in “text only” and was unusable. OWA still worked perfectly, just ECP was bad

I tried all sorts of tricks including deleting and rebuilding the EAC/ECP webroots in IIS using PowerShell scripts – nothing worked. Different browsers, compatibility mode etc.

Then I saw a blog post showing the FULL URL:

https://mail.company.com.au/ecp/?ExchClientVer=15

This worked! Using the /?ExchClientVer=15 part seems to have done the job and we can now hit that Ex2016 ECP/EAC pages from any browser again

I am not sure what happened but likely caused by the combination of having multiple Exchange on different versions and some update has now forced us to use this FULL URL incl ExchClientVer=15 statement.